Process and apparatus for makin chrome and similar steels



Sepi. 5, R933., K. M. slMPsoN PROCESS AND APPARATUS FOR MAKING CHROMEAND SIMILARST Filed April 16, les@ v of chromium steels.

ing in which:

Patented Sept. 5, i933 PROCESS im APARATTUS EGR ll' CHROME AND SER/HEARS'IllElElLS Kenneth M. Simpson, New York, N. Y. Application April i6,i930. Serial No. lleii e pimms.

My invention relates to a process and apparatus most particularlyadaptable to the making They may also be applied to the making of othersteels of high melting point.

Steels of the type of chrome steels are very diicult to melt, and in theprocess of making the same it is difficult to maintain the mass of metalunder treatment suiciently fluid throughout Without the use ofexcessively high temperatures, and a concomitant poor heat economy.

In my process I use an open hearth furnace for the manufacture of chromesteel, thefurnace being of the usual conventional design, exceptthat'there is disposed beneath the hearth a number of heating nues inaddition to the usual overhead heating ordinarily employed in openhearth processes. By the use of my particular apparatus and process Ihave found that I can overcome many of the disadvantages which areattendant upon the open hearth process for treating steels having highmelting points.

In `an ordinary openv hearth furnace all the heat which is imparted tothe metal is applied by burning gas, oil or other combustible matterabove the hearth. Chrome steels are difficult to melt and to maintain ina iiuid condition, and since the heat must be diffused throughout thebath of metal through the top surface of the metal in the conventionalprocesses, it is necessary to use temperatures far in excessv of thosenecessary to effect the proper working up of the steel. In my openhearth process I have arranged ues immediately beneath thel bottom ofthe furnace hearth so that 'heat may be supplied to the steel both atits upper and its lower surfaces. lThe heating of the ues is controlledindependently of that of the upper hearth, although the same source offuel may be used for both. By means of this independent control I canmaintain the temperature of theA bottom of the hearth at any desiredvalue. I prefer, however, to maintain a temperature difference ofapproximately 100 to 150 difference between the upper and-lower surfaceof the hearth, 'the upper surface of the hearth being maintained at thehigher temperature.

The type of furnace which I desire to use in my process is shown in theaccompanying draw- Figure 1 represents elevation in section of mypreferred form of furnace;

Fig. 2 is a plan view partially in section taken along the line 'A-A ofFig. l; and

(Cl. FJMS) Fig. 3 is a view taken along section B-B of Fig. l;

The furnace 1 is provided with a hearth 2 in which is a charge 3. Thefuel lines 4 and 5, preferably gas mains, may lead from the same 00source of fuel and are provided with controls for regulating the ow offuel. Fuel from conduit 6 leading from fuel line 4 is burned by means ofair Which enters at '1, and this combustion serves to heat the uppersurface of the 65 hearth and the metal under treatment-` The bottom ofthe hearth is heated by means of the burning of gas which enters throughconduit 8, into flues 9, air to support combustion being drawn throughopening l0. Bafes 1l are 70 interposed in the stream of fuel, thepurpose of which is apparent. The products of combustion both from theupper hearth and from the flues 9 are expelled through nue l2.

In my process for the production of chrome, steel the furnace is heatedand scrap metal is melted in the furnace and worked down until thecarbon contained therein is suitably low, that is .15% or less.Ferrochrome is then added to the molten mass of steel to give the`desired chrome content, which ordinarily will run from.

10 to 20%. When the ferrochrome is entirely melted and chromium hasbecome thoroughly intermingled throughout the mass of steel, the moltenmetal is 4tapped from the receptacle into 5 a ladle and run into ingotmolds. I maintain a temperature on the upper portion of the hearthordinarily at about 2900 F, the temperature within the flues at the`bottom of the hearth ranging from 2750 to 2800 F. I can 90 vary eithertemperature by virtue of the independent control of thefuel fed to theupper portion of the hearth and to the flues at the `bottom of thehearth. 'The temperature may 95 be very accurately controlled Withoutyany great degree of skill on the part of the. operator and the mass ofmetal being treated can be maintained at a substantially uniformtemperature throughout its mass. Thisv enables the temperature of themetal bath to be held Within a range which is not excessively elevatedover that necessary for the making of chrome steel, resulting in a veryefficient heat economy.

I claim as my invention: 105

1. In an open hearth process for producing chrome steel, the steps whichcomprise heating the steel at its upper surface from the primary sourceof heat, and simultaneously heating the steel from beneath its lowerportion from an 11'@ independently controlled heating source, the

which is controlled independently of the first y mentioned source ofheat.

3. The process described in claim 11 in which the temperature of theprimary heat source disposed above the steel is maintained from 100 to150 F. in excess of that of the auxiliary source disposed beneath thesteel.

KENNETH M. SIMPSON.

